Sewage treatment



Oct. 1,1941. f o. WAR@ y '2,258,398

SEWAGE TREATMENT Filed Sept. 30, 1939 T ATTORNEY,

Patented Oct. 7, 1941 UNITED STATES PATENT OFFICE 2,258,398 s'EwAGETREATMENT Oscar Ward, Marshfield, Wis.

Application September 30,v 1939, Serial No. 297,289

. 4 Claims.

are in suspension and in solution therein, and to release as a result ofthat removal, eiiluent thatl has been purled as to its oxygen demand.

'I'his invention relates to improvements in a process of treating liquidcontaining septical organic materials in which a trickling fllter-bedand clariiieris used. A trickling filter-bed as usually constructed isamass of discrete aggregatve particles of stone, cinders, or the likeover which sewage is distributed with the result that it tricklesdownwardly through the interstices of the bed and is discharged. Thediscrete particles are inoculated with aerobic biologic organismsranging from bacterial ora through protozoa. up to worms. y The biologicorganisms, which are herein sometimes referred to generically asbacteria although perhaps notv quite correctly, grow on the surface ofthe discrete material of the filter-bed. As they are of the aerobictype, air is anecessity for them. Also, as they eat all the time, andnot intermittently as do j vertebrates, a constant supply of food mustbel provided within easy reach of them for they are immotile. Because oftheir immotility, the end products must be removed from them.

As the bacteria pass through their life cycle, they tend to formjelly-like interfaces around the discrete filter media and thismay 'besaid to be zoogloea which is definable as a colony of bacteria forming ajelly-like mass" and also as bacteria held together by a matrix secretedby themselves.

It is` the tendency of bacteria in filter-beds to form this jelly thatapparently accounts for the occasional but often serious ponding orooding of filter-beds. In certain instances where a trickling filter-bedhas been supplied with sewage too rapidly, there has resulted such agrowth of` zoogloeal jelly, that the interstices between thediscrete'iilter mediums have become clogged and the applied liquid hasthus been prevented from percolating or trickling therethrough todischarge. Ponding, which means submergence of the filter-bed, can beserious for it tends to drown or otherwise kill off` the aerobicbacteria. If too many are killed off before the submergence is`overcome, it may be necessary to completely inoculate the bed anewbefore it can properly function again.

7 JUL 211942 (Cl. 21o-7) plied to the filter-bed, the bacteria. may notget enough food to continue their life cycle, especially when it isrecalled that they feed mees-- santly and must do so to live. I haveobserved that there is a tendency to clog in the upper regions of afilter-bed while this tendency is rarely encountered in the lower regionthereof. 'I'his has led to the conclusion that if the normal amount ofinilowing sewage supplied to the filter-bed is augmented withsewage thathas already passed through thefbed, several desirable results would beexpected. That is, by an augmented feed there would be (l) ample foodmade available to the bacteria, (2) the increased liow would flushdownwardly undue accumulations of jelly that would otherwise be clogging(and also harmful `to the bacteria because of their smothering action onthe bacteria), and (3) living bacteriawould be applied with the filterfeed in such a substantial quantity that the biologic activity in the'upper section would closely equal that of the lower section. Actualpractice indicates that my conclusions `were correct, when I passedfilter-bed discharge to a clariiier and used liquid from the clarifierto augment the amount of sewage being supplied to the filter-bed. j q Abasic aspect of the present inventionis directed to an improvedfilter-bed operation attained by closed-circuiting the filter-bed with aclarifier wherein liquid feed for treatment is cycled while beingytreated and from which end'- products of the treatment leave thecircuit as sludge along one path leading from the clarifier and fromwhich eiliuent that has had clarification and puriiication treatmentleads along another path.

An unexpected result of the operation of such a system'is that whereasheretofore all of the 40 biological purifying activity (or B. O. D.satisfaction) took place in the filter-bed, I have found that as aconsequence of the performing of this invention some of the purifyingacivity is transferred from the trickling filter` to the clarifier. Thismeans that there can be used an abnormally small filter-bed coupled incyclic arrangement with a spacious clarifier.

Such transfer of biologic activity or its extension and substantialexpansion into the clarier and the recycling of liquor undergoingtreatment as between the clarifier on the one hand and the filter-bed onthe other hand leads to the ensuring and maintaining of non-pcinding`condition for the filter-bed and to the continuing of condi- At the sametime,` if too little sewage 1s sup- 55 tions favorable to anuninterrupted passage of mirar-.a

sewage liquid therethrough inlall areas: thereof.

The uninterrupted and unobstructed fiow of liquid downwardly through thefilter-bed carries with it quantities of the living organisms that passwith the liquid infn the clarifier and with the same there is embodiedand carried enough dissolved oxygen to support and maintain their lifeprocesses even when in the body of liquid Within the clarier.

When liquid is recirculated between filter-bed and clarifier, as hereinproposed, I have found it highly desirable to use liquid material drawn`directly from within the clarifier rather than .its normal rate, itwill cause inflow to the clarifier to increase. and that will upset thedesigned detention capacity. If this be done, then the clarifier wouldhave to be designed with abnormal capacity to give it the full detentiontime under all conditions. By recirculatinlg from within the clarifiereven though large quantities be used, the detention capacity of theclarifier is not changed for the effluent outflow is always constant.

This returned or recycled tank liquor serves to carry back to thefilter-bed septical organics that have not yet been stabilized orrendered innocuous. Thisl material comprises food for the bacteria inthe bed, and at the same time, it also comprises nuclei that, when anon-biologic solidscongregative stationis used, have the property ofattracting other solids thereto and thus conditions are favorable to thedesired coagmentation or coagulation thereof into settleable condition.

Other objects and aspects of the invention will become apparent from thesucceeding portions ofthe specification.

As illustrative of certain manners in which the invention may berealized reference is made to the corresponding drawing whichconstitutes a part of this specification.

In said drawing:

Figs. 1 and 2 diagrammatically illustrate an arrangement embodying .thisinvention wherein there is indicated a clarifier that receives thefilter eiiluent and according to which a 'part of the sludge or materialwithin the clarifier is withdrawn from the interior of the clarifier,and the sludge or material thus withdrawn provides a part of thefilter-bed feed in that it returns to the liquid being fed to thefilter-bed at a point ahead of the filter.

Fig. 3`diagrammatically illustrates a complete sewage disposal systemwherein important features of the invention are embodied and employed.In this figure there is included or indicated not only the filter andclarifier, that receives the filter discharge, but also other units orinstrumentalities which may be effectively employed in the system, forexample, a preliminary or primary clarifying means located` ahead of thefilter, flocculat'ing means for conditioning liquid on its way to thefilter, to wit, ahead of a second or intermediate clarifier between theprimary clarifier and trickling filter. Therein there is also indicateda chemical dosing ahead4 over which the incoming sewage supplied theretofor treatment is relatively uniformly distributed as by means of adistributing mechanism generally designated by 22 and which may be ofthe travelling arm type, a spray nozzle type, or any other suitabletype. 'I'he filter 2| is a trickling filter, the bed thereof is providedby an assemblage of discrete material as by an aggregate of brokenstones, slag, coal or the like, and the sewage treated thereupontrickles down through the nterstices in the presence of air. Biologieorganisms and zoogloea jelly-like interfaces form -or collect upon theaggregates in the filter-bed and winch with proper filter operationcontinue to exist in the filterbed. The functioning of this type offilter is well known. The filter effluent or discharge passes outwardlyalong the path 23. The path 23 lads into a. sedimentation zone orclarier of the type diagrammatically shown in Fig. 1 and in verticalcross section in Fig. 2. This clarifier is of the DORR. or equivalentmechanically cleaned type, provided with traveling sludge rakes, plowsor scraper 24a adapted for the impelling to discharge through path M ofsolids settling or depositing on the bottom of the clarifier in the formof sediment or sludge. The clarifier is indicated as being of thecross-now type provided with an iniiuent launder 24h and an overfiow `oreffluent launder or outlet 24e. Other types of clarifiers may be used solong as for the clarifier or sedimentation zone there extends a path ofinfiuent therefor; a path for overflowing clarified supernatant eiiiuenttherefrom; a path for the discharge of settled sludge; and meansforreturning material from the clarifier either directly or indirectlyback to the filterbed.

In the realization of the present invention some of the filter eiiiuentis withdrawn or diverted from the path 23 which may be viewed asincluding the clarifier 24, that is, liquid is withdrawn from the path23 or from the parts into which path 23 leads. The withdrawing ordiverting of filter discharge may be along a path such as 28 in Figs. 1and 2, or a path such as 2B in Fig. 3. The diverted or withdrawn liquidis transferred or lifted in appropriate amount by suitable means, as forexample, centrifugal pump 21 which controllingly delivers the withdrawnmaterial along a path such as-33 of Figs. 1 and 2, or such as 29, 3|, or33 of Fig. 3 dependent upon which path or line is opened and alsoaccording to the type of recirculation desired for a par- .ticularperiod.

The small crosses in each of the several lines,

pipes or conduits indicate positionable control p valves which are openor closed, or otherwise certain of such valves which are designated as30, 32 and 34 are respectively located in the pipes. lines or conduits28, 2l and 33. 'I'he pipe or line 33 constitutes a return leading backto point Illa at the head end of the system in the arrangement of Figs.1 and 2. This point Illa is in the sewage supply line leading directlyto the trickling filter. In the system of Fig. 3 pipe or line 33constitutes a `return to point Illa in line l leading to a. primary orpreliminary clarifier, pipe or line 3i is a return leading back to apoint I2a which is in a line I2 leading directly to a `fiocculationstation I3 which is between the primary clarifier II and theintermediate clarifier I1 and the pipe or line 23 is a return lineleading to the point 20a which is in line 20 leading directly to thefilter.

By these return lines, tank liquor is returned to the system where it orsubstantial quantities .thereof are ultimately distributed by means ofmechanism 22 over the entire filter-bed for retreatment, ugmentlng theinflowing sewage passing to the filter-bed for treatment thereby.

The tank liquor obtained from the clarifier 24 passes through the mediumof a pipe such as 28 or part 26e of pipe 26 leading from a lower portionof the clarifier. This withdrawal of tank liquor is 'by means of pipes28 or 26, as the case may be, and is from a locality within theclarifier that` is functionally remote from the effluent overflowlaunder or clarifier efiiiient outlet 24e. In the instance of thearrangement of Figs. 1

'and 2r this tank liquoris shown as being used to augment the new feedor polluted liquid incoming to` the system through the path Il). Thefilter-bed 2| and the clarifier 24 thus may be said to be closedcircuited in that material `from the clarifier is passed backA to andthrough the filter-bed to the clarifier again. Claried supernatantpasses from the clarifier or from the system through the launder 24c andpipe 25 referred to. Settled sludge or sediment can be passed from theclarifier or from the system as through pipe 44 leading from the lowerportion of the clarifier. The clarifier, as the name implies, must havea liquid retention capacity large enough for suspended solids in theliquid fed thereto to settle therein' and form a lower layer of sludgeand an upper overlying layer of clarified supernatant liquid.

According to the system of Fig. 3 the incoming sewagepasses along-thepath I0 to the place where it enters a primary clarifier Il- Theeffluent from the primary clarifier Il passes along the path I2 topreliminary treating apparatus which includes a fiocculation zone I3 anda second or intermediate clarification or sedimentation zone I1. Fromthe preliminary treating apparatus just referred to, the effluent fromthe intermediate clarifier I1 enters and flows along pipe or line I8 toand through a dosing device I9, for supplying to the eiiluent if or whendesired a chemical for coagulating solids therein, and from the dosingdevice I9 the liquid passes along the line or pipe 20 to the influentend of the trickling filter 2 I. The filter 2i is of the tricklingfilter type functioning as previously described `and the incomingsewage-or incoming sewage materialis distributed over `the bed 2Ia ofthis filter by the distributing mechanism 22. The

filter discharge passes from the filter 2i along the path 23 into theclarifier 24 from which any portion of the contents of the clarifier iswithdrawn and passed `to the incoming sewage or sewage material at any`point en route to the filter 2| whereby the withdrawn and returned '75.

portion from the'liquid from the clarifier 24 is passed to andultimately distributed over the bed of the filter 2| for the purpose ofseeding the latter and also as an augmentive supplied with the liquidportion fiowing to the filter for its initial treatment therein.According to the arrangement of Fig. 3 the preliminary treatingapparatus comprises a tank or basin I3 provided with occulationmechanism. The -function of this preliminary treating apparatus is totreat or agitata the incoming sewage efiluent in such a maner thatflocculation takes place and is effected, some prior tothe distributionof the sewage material over the filter-bed and some during the periodwhile the sewage material undergoing treatment is passing through thebed of the filter. The apparatus I3 is indicated as having fiocculationpaddles I4 and a valve controlled air supply I5 either or both of whichmay be used for gently agitatlng the sewage liquid in the tank I3 in amanner favorable for carrying out and realizing fiocculating operationthat rel sults in the development and amassment of settleable fiocs andfioc colonies formed of solids that are suspended in the liquid.According to Fig. 3 the liquid content from I3 passes along the path I6into the intermediate clarifier I1 from the latter of which, aspreviously indicated, the liquid passes along the path I8 through thedoser-wherein it may or may` not be dosedand ultimately to and into thefilter 2 I.

From one point of view the clarifier I1 may liquid derived from theclarifier `24 through the l medium of .pipe 28 in Fig. 2` and throughthe medium of pipe 26 that has valve control branches 26e and 26d ofFig. 3. The clarifier 24 when embodied in an arrangement like thatillustrated by Fig.` 3 is properly referred to as a secondary clarifieror secondary sedimentation tank and is sometimes herein referred to assuch. When branch 26e is open and 26d is closed tank liquor is withdrawnfrom the secondary sedimentation tank 24 by means of the pump 21 and isdelivered l to the incoming sewage as through the pipe 23 which isopened or closed or otherwise controlled by valve 30, pipe 3| which isopened or closed or otherwise controlled by valve 32, and/or pipe 33which is openedlor closed or otherwise controlled by the valve 34. Itwill thus be seen that dependent upon winch one or more of these valvesis left` open, a part of the filter discharge can be returned to any oneor more of the points Illa, I2a or 20a, as the case may be, namely, tothe polluted liquid that is on itsway to the primary clarifier; to thesewage efliuent passing from the primary clarifier; or to the effluentfrom the intermediate clarifier preparatory to introduction into thefilter. lLikewise, if the valve of pipe 26e is closed and the valve ofpipe 26d is open, it willbe evident that the eiliuent from the secondarysedimentation tank or `clarifier can be 'y passed to any one or more ofthe locations just mentioned whereby the effluent from the secondarysedimentation tank will provide that portion of the filter effluentwhich is ultimately returned to the filter for the purpose of seedingthe llterbed or for serving as material for augmenting the rest of theliquid iiowing thereto.

According to the system of Fig. 3 the sludge from the primary clarifierIl passes along the path 36 and 40 and is pumped by pump 4I along path42 into a digester 43. According to the system of Fig. 3 there is alsoprovided a path 38 leading to the entrance side of this pump 4I wherebysludge from the intermediate clarifier l1 can also be passed into thedigester 43. 'I'he pipe or path 36 can at will be closed or opened bymeans of valve 31 and likewise the pipe or path 38 can be opened orclosed by the valve 39.

Some of the sludge, in fact a main portion of the sludge, from thesecondary clarifier 24 of Fig. 3 can be passed therefrom through thepipe 44 by operating the pump mechanism which includes pipe 44, pump 45and pipe 46.

From what has preceded, it is manifest:

That recirculation of tank liquor (the liquid within the clarifier) in asewage treatment filterbed system, (1) enables a smaller clarifier to beused without sacrificing effective detention capacity thereof; (2)expands or extends the biologic activity .beyond the filter-bed itselfinto the clarifier; (3') prevents the premature release of unstabilizedsolids from the system by assuring repeated exposure thereof to thenecessary biologic action; (4) functions in augmenting the raw sewagefed to the filter-bed to give rates of liquid application to thefilter-bed that fiush the accumulations of jelly from the intersticesbetween the filter-bed media and thus prevent clogging and consequentponding; (5) functions in supplying ample food to the immotile-bacteriawhile constantly removing therefrom their end products or excrescenciesand to thus prevent smothering; (6) enables the active biologicconcentration to be substantially as great in the upper section of thefilter-bed as in the lower and thus be made more uniform; and (7)provides nuclei which, when a fiocculation or chemy ical dosing stationis used, attract other suspended solids and thus aid in thecoagmentation or coagulation thereof into larger solids.

That the Yuse of 'a suspended-solids congregating station, that makesuse of chemical coagulation or mechanical coagmentation, ahead `of thefilter-bed, relieves the bacteria of such work which -lets themconcentrate on the purification and stabilizing of the putrescible orseptical organics, which results in the possibility of using a smallerfilter-bed to the. extent of from ten to fifteen percent less size thanis normal.

That the use of mechanical fiocculation as a solids-congregating deviceavoids the recurring cost of chemicals for a chemical precipitationstation, and has the added advantage of producing integrated `fiocs thathave been conditioned for settleability, which aids in the removalthereof from the system by means of quiescent sedimentation. Also theagitation of flocculation type. As this System is designed yfor treatingliqluids that are polluted with septical or putrescible organics, everyprecaution must be taken to remove these solids from the systemsubstantially as soon as they are deposited in the form of sludge in theclarifier that is .closed circuited with the filter-bed.

An unexpected advantage of the practice of this invention is that itkeeps down, if not obviates, the fiy nuisance that before my inventionwas considered inevitably concomitant with filter-bed operation.

This patent matures from a patent application that was a continuation inpart of my parent patent application Serial No. '704,954 filed January2, 1934,

I claim:

1. The method of treating liquids polluted with Afier, and augmentingthe liquid passing to the filter-bed with liquid bearing activeorganisms taken from the clarifier direct to the filter-bed in amountsufficient to fiush continually zoogloeic accumulations from thefilter-bed thereby insuring against their developing to clogging proporltions and also keeping vitalized the aerobic biologic organismsfunctioningwithin the filter-bed While-at the same time conveying fromthe filterbed into the clarifier quantities of such living organismswhereby certain biologic satisfaction of 1oxygen demand is alsocontinued within the clari- 2. The method of treating liquids pollutedwith septical organi-cs, which comprises continually supplying anddistributing incoming fresh liquid so as to receive an initial butpartial biologic treatment in an aerobic biologically-active tricklingfilter-bed, passing filter-bed discharge containing putresciblesettleable organic material to a clarifier horizontally spaced from thefilter-bed for holding a body of liquid in quiescent condition favorablefor the deposition of settleable solids and having an overflow ofsupernatant clarified liquid efliuent, removing and discarding depositedmaterial from the clarifier before septic conditions should becomeestablished within the clarifier, and augmenting liquid being suppliedfor biologic treatment with tank liquor from the clarifier containingactive biologic organisms and organic matter thus providing augmentingorganisms and nutriment which furthers biologic development within thebed and which also supplies an augmenting flow sufficient in volume forassuring the washing of biological excretions from the gel interfacesWithin the filter-bed and thereby functioning to avoid the developmentof excessively large gel interfaces within the filter-bed.

3. 'I'he method of continuously treating liquids polluted with septicalorganics, which comprises supplying inflowing liquid to a tricklingfilter-bed and distributing it thereupon to be treated therein byaerobic biologic organisms for satisfying oxygen demand of the septicalorganics, passing filter-bed discharge to a clarifier horizontallyspaced from the filter-bed and holding a body of i matassa liquidinquiescent condition conducive'to the sedimenting of suspended solidsand having `overl flow oi. supernatant clarified liquid, removing and`discarding organic sediment from the clarifier i'or preventingsepticity within the clarier, withdrawing tank liquor containing organicmatter from the clarifier and augmenting the iniiowing liquid withwithdrawn tank liquor suincient in quantity to insure flushing of theinterfaces to `discourage clogging and for keeping vitalized thebiologic organisms operating in the filterbed while at the same timeconveying from the filter-bed in the discharge thereof passing to thequiescent liquid quantities oi.' living organisms whereby biologicsatisfaction of oxygen demand is continued from the filter-bed tosubstantially within the quiescent liquid to` an extent thatmactiveorganisms are transferred from the quiescent liquid back to the liquidbeing treated in the illt'er-bed. i

4. The method of treating liquids polluted with septical organics, whichcomprises supplying liquid to a biologically active trickling illter-bedto be`- treated therein by aerobic biologic organisms of zoogloeicinterfaces in the trickllng filter-bed Y `for satisfying certain of thebiological oxygen demand of the septical organics, passing filterbeddischarge to a clariiler horizontally spaced from the filter-bed andhaving an overflow of clarified emuent, removing sediment from theclarifier to avoid septicity in the liquid contents of the clariiler andcontinually augmenting the liquid passing to the illter-bed withliquid-bearing active organisms taken from the clarler to the filter-bedin amount suilicient to ilush continually zooglceic accumulationsfromthe nlterbed thereby insuring against their developing to cloggingproportions and also keeping vitalized the aerobic biologic organismsfunctioning within the filter-bed while at the same time conveying fromthe lter-bed into the clariiler quantities oi' such living organismswhereby certain bio- 0 logic satisfaction oivioxygen demand is alsocontinued within the clarier. t

OSCAR WARD.l

